On the page titled;
Mozilla Firefox, Portable Edition 20.0.1 (web browser) Released
Submitted by John T. Haller on April 12, 2013 - 10:42am
Note that Windows 2000 is no longer supported by Firefox. You can still use Firefox ESR for another month, though.
The linked page is;
Mozilla Firefox ESR, Portable Edition
Firefox Logoyour browser, to go™
Download Mozilla Thunderbird ESR, Portable Edition
Version 17.0.5 for Windows, English
18MB download / 34MB installed (Details)
However it does not run on my computer witn "Microsoft
Windows 2000 [Version 5.00.2195]". So the first page seems
to be in error. And I would like to obtain a working version.